以五常、常熟和雅安水稻土为研究对象,通过室内泥浆培养,利用基于膜进样质谱仪(Membrane Inlet Mass Spectrometer,MIMS)的15N示踪技术,探究了温度、pH、NO_(3)^(–)浓度、C/N、Fe^(2+)和S2–浓度对三种水稻土反硝化和硝酸根异化还原成...以五常、常熟和雅安水稻土为研究对象,通过室内泥浆培养,利用基于膜进样质谱仪(Membrane Inlet Mass Spectrometer,MIMS)的15N示踪技术,探究了温度、pH、NO_(3)^(–)浓度、C/N、Fe^(2+)和S2–浓度对三种水稻土反硝化和硝酸根异化还原成铵(Dissimilatory nitrate reduction to ammonium,DNRA)速率及二者占硝酸根还原过程相对贡献的影响。结果表明,在所研究的稻田土壤中,反硝化是NO_(3)^(–)异化还原过程的主导途径,占比87.97%~91.73%,而DNRA仅占8.27%~12.03%。反硝化和DNRA速率随温度升高均呈指数增长,且DNRA占NO_(3)^(–)异化还原的比例(RDNRA)也随温度升高呈增长趋势。反硝化和DNRA速率分别在pH为7或者8.5时最高,相对于碱性环境(4.92%~14.67%),酸性环境中RDNRA(6.24%~15.56%)更高。反硝化和DNRA速率与NO_(3)^(–)浓度之间关系符合米氏方程,且反硝化的最大速率(Vmax)和米氏常数(Km)均大于DNRA。与未加碳源对照组相比,C/N为2.5时,反硝化速率显著提高了22%~35%;C/N大于2.5时,DNRA速率显著提高了74%~199%。三种土壤中,Fe^(2+)添加和S2–添加处理中呈现出类似的趋势,均在低浓度电子供体(即Fe^(2+)和S2–浓度分别为300~500μmol·L^(-1)和50~62.5μmol·L^(-1))时呈现出最高的反硝化速率,而DNRA速率达到峰值则需要更高浓度的电子供体(即Fe^(2+)和S2–浓度分别为800~1000μmol·L^(-1)和100~125μmol·L^(-1))。综上可知,环境因子可显著影响NO_(3)^(–)异化还原过程的速率及分配,其中高温、高C/N、高浓度Fe^(2+)和S2–有利于更多的NO_(3)^(–)分配给DNRA过程,而高浓度NO_(3)^(–)会提高NO_(3)^(–)向反硝化过程的分配。上述研究结果深化了对水稻土NO3–异化还原过程分配的认识,对于探寻潜在农学措施提高DNRA过程的分配比例,进而提高土壤中氮素的固持和提高稻田氮肥利用率具有重要的科学意义。展开更多
Molecular imprinted polymer membranes (MIM) combine the merits of molecular imprint and membrane technology. In this work, a very thin of imprinted polymer that can specifically and selectively absorb the basic templa...Molecular imprinted polymer membranes (MIM) combine the merits of molecular imprint and membrane technology. In this work, a very thin of imprinted polymer that can specifically and selectively absorb the basic template (adenine) was grafted on the surface of polyvinylidene fluoride membrane by photo-grafting copolymerization. Because the molecular imprinted polymer is grafted on the surface of the matrix membrane without blocking the membrane pores, the resultant MIMs have high flux as microfiltration membrane (0.26 mol·m^-2·h^-1 of template and flux for distilled water was 3.6 ml·mim^-1·cm^-2 at 0.8 MPa). Moreover, the MIMs can absorb/desorb template molecules rapidly. Usually, it only takes several minutes for MIMs to absorb more than 75% of the template (adenine) in aqueous solution. And the influences of the type and amount of the functional monomers, the amount of the cross-linker on the absorption capability are discussed to determine the optimal preparation conditions。展开更多
Molecularly imprinted microspheres (MIMs) of D-mandelic acid were synthesized in this study. Chloromethylated polystyrene beads modified with iniferter were used as supports for photo-grafting of a molecularly imprint...Molecularly imprinted microspheres (MIMs) of D-mandelic acid were synthesized in this study. Chloromethylated polystyrene beads modified with iniferter were used as supports for photo-grafting of a molecularly imprinted polymer (MIP) layer. The polymers were characterized by FT-IR, elemental analysis and thermo-gravimetric analysis to testify the polymer formation and its thermal stability. Scan- ning electron micrographs (SEM) show that the MIP particles are mono-dispersed and well-spherical, with the average diameter of 4.38 μm and size distribution coefficient of 1.02. Furthermore, the MIMs were packed in a stainless steel column and evaluated as stationary phases in high performance liquid chro- matography (HPLC). The prepared MIP exhibited a considerable capability of chiral separation between template and its enantiomer. Accordingly, this kind of MIP is likely to have wide applications in chemical sensing, chromatographic analysis and solid phase extraction.展开更多
利用HIDEN公司HPR40溶解气体质谱分析仪,通过实验探索和实际应用,建立了连续走航高频率同时测定海水中O_2、Ar和CO_2等多种气体的分析方法。通过选择硅树脂膜的循环水取样器、进样流量为220 m L/min、进样平衡温度低于海水2℃等实验条件...利用HIDEN公司HPR40溶解气体质谱分析仪,通过实验探索和实际应用,建立了连续走航高频率同时测定海水中O_2、Ar和CO_2等多种气体的分析方法。通过选择硅树脂膜的循环水取样器、进样流量为220 m L/min、进样平衡温度低于海水2℃等实验条件,建立了船载连续走航系统,实现了利用膜进样质谱仪(MIMS)连续走航测定表层海水O_2/Ar比值和p CO_2。所用仪器稳定性良好,连续测定12 h大气鼓泡48 h后的海水样品获得O_2、Ar和CO_2的精密度分别为1.57%、3.75%和2.21%,O_2/Ar的精密度为2.61%;该方法的重复性好,10 d内绘制7条CO_2工作曲线斜率的相对标准偏差RSD=4.18%。应用该方法在南海北部陆坡19.8°N^20.8°N,114.7°E^115°E断面进行调查并取得了很好的效果,结果表明:该调查断面的生物氧过饱和量Δ(O_2/Ar)为0.56%±1.02%,其变化范围为-2.52%至3.34%,调查断面的pCO_2值为361.53±40.46μatm。该方法具有直接、快速、高时空分辨率测定多种溶解气体的优点,为认识多组分气体的高分辨时空分布格局,深入开展我国陆架边缘海生物过饱和氧、海洋群落净生产力和pCO_2动力学研究提供了新方法。展开更多
文摘以五常、常熟和雅安水稻土为研究对象,通过室内泥浆培养,利用基于膜进样质谱仪(Membrane Inlet Mass Spectrometer,MIMS)的15N示踪技术,探究了温度、pH、NO_(3)^(–)浓度、C/N、Fe^(2+)和S2–浓度对三种水稻土反硝化和硝酸根异化还原成铵(Dissimilatory nitrate reduction to ammonium,DNRA)速率及二者占硝酸根还原过程相对贡献的影响。结果表明,在所研究的稻田土壤中,反硝化是NO_(3)^(–)异化还原过程的主导途径,占比87.97%~91.73%,而DNRA仅占8.27%~12.03%。反硝化和DNRA速率随温度升高均呈指数增长,且DNRA占NO_(3)^(–)异化还原的比例(RDNRA)也随温度升高呈增长趋势。反硝化和DNRA速率分别在pH为7或者8.5时最高,相对于碱性环境(4.92%~14.67%),酸性环境中RDNRA(6.24%~15.56%)更高。反硝化和DNRA速率与NO_(3)^(–)浓度之间关系符合米氏方程,且反硝化的最大速率(Vmax)和米氏常数(Km)均大于DNRA。与未加碳源对照组相比,C/N为2.5时,反硝化速率显著提高了22%~35%;C/N大于2.5时,DNRA速率显著提高了74%~199%。三种土壤中,Fe^(2+)添加和S2–添加处理中呈现出类似的趋势,均在低浓度电子供体(即Fe^(2+)和S2–浓度分别为300~500μmol·L^(-1)和50~62.5μmol·L^(-1))时呈现出最高的反硝化速率,而DNRA速率达到峰值则需要更高浓度的电子供体(即Fe^(2+)和S2–浓度分别为800~1000μmol·L^(-1)和100~125μmol·L^(-1))。综上可知,环境因子可显著影响NO_(3)^(–)异化还原过程的速率及分配,其中高温、高C/N、高浓度Fe^(2+)和S2–有利于更多的NO_(3)^(–)分配给DNRA过程,而高浓度NO_(3)^(–)会提高NO_(3)^(–)向反硝化过程的分配。上述研究结果深化了对水稻土NO3–异化还原过程分配的认识,对于探寻潜在农学措施提高DNRA过程的分配比例,进而提高土壤中氮素的固持和提高稻田氮肥利用率具有重要的科学意义。
文摘Molecular imprinted polymer membranes (MIM) combine the merits of molecular imprint and membrane technology. In this work, a very thin of imprinted polymer that can specifically and selectively absorb the basic template (adenine) was grafted on the surface of polyvinylidene fluoride membrane by photo-grafting copolymerization. Because the molecular imprinted polymer is grafted on the surface of the matrix membrane without blocking the membrane pores, the resultant MIMs have high flux as microfiltration membrane (0.26 mol·m^-2·h^-1 of template and flux for distilled water was 3.6 ml·mim^-1·cm^-2 at 0.8 MPa). Moreover, the MIMs can absorb/desorb template molecules rapidly. Usually, it only takes several minutes for MIMs to absorb more than 75% of the template (adenine) in aqueous solution. And the influences of the type and amount of the functional monomers, the amount of the cross-linker on the absorption capability are discussed to determine the optimal preparation conditions。
基金This work was supported by the National Natural Science Foundation of China(Grant No.60121101).
文摘Molecularly imprinted microspheres (MIMs) of D-mandelic acid were synthesized in this study. Chloromethylated polystyrene beads modified with iniferter were used as supports for photo-grafting of a molecularly imprinted polymer (MIP) layer. The polymers were characterized by FT-IR, elemental analysis and thermo-gravimetric analysis to testify the polymer formation and its thermal stability. Scan- ning electron micrographs (SEM) show that the MIP particles are mono-dispersed and well-spherical, with the average diameter of 4.38 μm and size distribution coefficient of 1.02. Furthermore, the MIMs were packed in a stainless steel column and evaluated as stationary phases in high performance liquid chro- matography (HPLC). The prepared MIP exhibited a considerable capability of chiral separation between template and its enantiomer. Accordingly, this kind of MIP is likely to have wide applications in chemical sensing, chromatographic analysis and solid phase extraction.
文摘建立了一套针对由金属伪影造成的CT图像质量退化的恢复算法。利用Non-Local前置滤波(Non-Local Pre-filter,NL-PF)对原始CT图像进行全局滤波,从而有效地滤除原始图像中的噪声并对射线状金属伪影进行了平滑,其后配合最大互信息量分割算法(Mutual Information Maximized Segmentation,MIMS)从图像中分割出伪影成份,并利用其周围非伪影部分的像素对伪影类像素进行插值处理得到一个称之为"伪组织"类的图像。最后,通过融合"伪组织"图像的sinogram和原始CT图像的sinogram,得到校正的sinogram并采用滤波反投影重建算法完成金属伪影的CT校正图像。利用所提出的方法可以对含有金属伪影的CT图像进行有效伪影消除,其中射线状伪影消除效果显著。另外,此方法还可以锐化器官轮廓,避免了临床上由于金属伪影导致的放射治疗效果下降。实验表明,金属伪影消除算法可以有效地消除高密度物体造成的金属伪影,从而提高临床诊断和治疗的效果提供技术支持。
